Purification of chlorobutyronitrile

Abstract

Chloro alkyl nitriles containing from about 3 to about 7 carbon atoms, such as chlorobutyronitrile, are produced in high purity by reacting the corresponding bromochloro alkane, typically 1-bromo-3-chloropropane, with alkali metal cyanide or alkaline earth metal cyanide in an aqueous system in the presence of catalyst of the formula (R).sub.4 MX wherein M is a Group V-A element; one, two or three of the R groups are lower alkyl having from 1 to about 4 carbon atoms, or phenyl; each of the other R groups is alkyl having from 2 to about 20 carbon atoms, or phenyl; X is a compatible anion such as chlorine, iodine, or bromine atom or a hydroxyl group. Such catalysts, especially tributyl methyl ammonium chloride, bromide, or iodide are effective during the reaction and are readily removed from the product after the reaction. Organic phase product from this reaction is purified in a sequence of several steps. Preferably, it is washed with water to remove at least a part of the residual catalyst present therein. Then the washed product is subjected to distillation to remove unreacted bromochloro alkane. After distillation, contaminant bromo alkyl nitrile is converted to chloro alkyl nitrile by a reaction with a water soluble chloride salt in the presence of catalyst of the foregoing type, additional catalyst being added if necessary. Following the last reaction, the aqueous and organic phases are separated removing the bromine as the bromine counterpart of the water soluble chloride salt used in the last reaction and the product is again washed with water to remove at least part of the catalyst used in the purification reaction.